1. Field of the Invention
The present invention relates to a heat exchanger for a gas boiler, and more particularly to a stacked-up type heat exchanger for a gas boiler wherein a plurality of plates are stacked up to construct a combustion gas flue for carrying exhaust gas, a hot/cold-water tube for supplying cold-water and for heating the same, and a return heating-water inlet for supplying heating-water.
2. Description of the Prior Art
In a conventional hot-water storage type gas boiler, a heat exchanger comprises a cylinder with a plurality of pipes therein to carry fresh water from the lower portion to the upper portion, a heating-water outlet and a return heating-water inlet disposed at the upper portion and the lower portion of the cylinder respectively, and a burner therebeneath for heating water. U.S. Pat. Nos. 4,432,307 and 4,644,904 disclosed heat exchangers used in such a hot-water storage type gas boiler.
FIG. 1 is a front sectional view for showing one of the embodiments of such a conventional heat exchanger for a hot-water storage type gas boiler as mentioned above.
According to FIG. 1, a heat exchanger 1 includes a heating-water heating portion 3 for heating and storing heating-water and a hot-water pipe 4. Inside heating-water heating portion 3 a plurality of flues 2 vertically passing through heating-water heating portion 3 are provided to carry high temperature exhaust gas. At an upper portion of the outer wall of heating-water heating portion 3 a heating-water outlet 31 for delivering high temperature heating-water is provided and a return heating-water inlet 30 is disposed at the lower portion thereof.
Hot-water pipe 4 made in a helical hot water pipe is disposed around the inner periphery of heating-water heating portion 3 to thereby make a heat exchange between hot/cold-water and heating-water. Hot-water pipe 4 also includes a cold-water inlet 40 and a hot-water outlet 41 at the lower and upper portions of heat exchanger 1 respectively so that hot/cold-water can come in and out heating-water heating portion 3. At cold-water inlet 40 a supplementary water valve 9 is provided for supplying heating-water with supplementary water.
At the lower portion of heat exchanger 1, a gas supply pipe 7 and a manifold 8 for jetting supplied fuel through gas supply pipe 7 to combustion points. In addition, a baffle, not shown in FIG. 1, is provided inside flue 2 to delay the flow of exhaust gas so that more heat is transferred to heating-water. An exhaust hood 6 is mounted on heat exchanger 1 to suck the exhaust gas risen through flue 2.
According to the heat exchanger for a boiler constructed as above, an high temperature exhaust gas is generated by burning the gas blown from manifold 8. The exhaust gas enters into flue 2 through a bottom surface of heat exchanger 1. At this time, the exhaust gas rising up through flue 2 exchanges heat with heating-water by way of the wall of flue 2. As such, the temperature of heating-water increases and hot-water pipe 4 located within in the heating-water is also affected by the heat.
Cold-water entering into heat exchanger 1 through cold-water inlet 40 is affected by the heat while passing through hot-water pipe 4 and thereafter high temperature water is delivered out of heat exchanger 1 through hot-water outlet 41. Exhaust gas that has passed through flue 2 is concentrated at exhaust hood 6 and is exhausted out of a boiler.
However, according to the conventional heat exchanger for a hot-water storage type gas boiler constructed as above, since flue 2 and separate hot-water pipe 4 are installed in heat exchanger 1, the welding process in manufacturing the heat exchanger is very difficult and the manufacturing time is prolonged accordingly. Also, in order to increase the thermal efficiency in such a heat exchanger, a larger-sized heat exchanger is required, accordingly high manufacturing cost and low productivity can not be avoided.